Load disconnecting switch especially for use in motor vehicles

ABSTRACT

A load-disconnecting switch has a permanent-magnetic holding circuit. A coil ( 5 ), upon excitation thereof, generates a magnetic flux that is opposite to the magnetic flux of the permanent magnet ( 9 ). The armature ( 6 ) is biassed to an open position by an armature spring ( 10 ), so that the armature spring ( 10 ), when a defined operational excitation is exceeded, detaches the armature ( 6 ) from the core ( 7 ) of the magnet system, allowing said armature to open and thereby disconnecting a switching contact ( 15 ) and a fixed contact ( 16 ). The load-disconnecting switch can be switched on again by means of a spring clip ( 12 ) acting on said armature ( 6 ).

The invention relates to a load-disconnecting switch, in particular forthe load circuit of a vehicle battery, in which the load circuit can bedisconnected automatically via an electromagnet system.

In motor vehicles, it is desirable in specific disturbance situations todisconnect the on-board network to a dead state abruptly. Such casesare, for example, a short in the load circuit that may lead to batterydischarge or vehicle burning, wrong polarization in the event ofstarting aid which may cause damage to the battery, but also destructionof the electronic systems in the on-board network, or a collisionaccident which may also cause shorts with a resulting risk of burning.

The document DE 41 10 240 C1 already discloses a means for providingprotection to a main current path in a motor vehicle. A disconnectsituation is determined by various sensors and comparison means andevaluated for disconnecting the circuit. This document mentions asdisconnect means, for example, an explosive cap or an electromagneticactuator, without the construction and function of such an actuatorbeing discussed in more detail.

The document DE 197 01 933 C1 reveals a load-disconnecting switch forthe load circuit of a vehicle battery, in which a contact arrangement isconnected between a pole terminal and a load circuit. In case ofoccurrence of a disturbance situation, the contact arrangement isunlocked via an electromagnet system and the circuit is interrupted.This known load-disconnecting switch comprises an arrangement having acontact rocker with a comparatively large number of individual partsnecessitating corresponding manufacturing expenditure and volume.

It is the object of the present invention to provide aload-disconnecting switch that is of simple construction, does notswitch unintentionally even in case of high accelerations and is of lowvolume.

According to the invention, this object is met with a load-disconnectingswitch comprising:

a housing having a base and a housing cover,

a magnet system having a coil, a core arrangement and an armature, thecore arrangement having a permanent-magnetic section exerting a holdingforce through which the armature is attracted to pole areas of the corearrangement, and said magnet system being adapted to be excited contraryto said permanent-magnetic section,

an armature spring biasing the armature to an open position, with theholding force of the permanent-magnetic section with attracted armaturebeing higher than the spring force of the armature spring,

a contact system having a contact spring, a switching contact arrangedon the contact spring and a fixed contact cooperating with the switchingcontact,

first and second connecting conductors extending out of said housing forconnection of the switching contact and the fixed contact.

An essential element of the load-disconnecting switch is thepermanent-magnetic section of the core arrangement. It has the effectthat the magnetic circuit has an attracted armature in the rest stateand, thus, has no movable parts in the rest state having no holdingforce applied thereto. This has the advantage that the constructionprovides particular strength with respect to acceleration. In case ofuse as a battery disconnecting switch in a motor vehicle, it is ensuredthat also in case of high acceleration forces, e.g. in an accidentsituation, the load-disconnecting switch is not triggered prior to theairbag. Moreover, in case of accidental dropping during assembly, therisk of damage to the movable parts is reduced. Electric excitation ofthe coil causes release of the armature, since the excited coilgenerates a magnetic flux opposite to the magnetic flux generated by thepermanent magnet. Consequently, the matching spring force of an armaturespring is sufficient for opening the armature. The use of a permanentmagnet as holding member permits the necessary driving power to be keptvery low. In this manner, it is possible to realize a particularlycompact constructional volume.

In an advantageous embodiment, additional mechanical locking isprovided. The necessary release force may thus be reduced further. Inaddition thereto, this locking provides for increased strength withrespect to acceleration.

In a preferred embodiment, the armature spring has an extension in theform of a spring clip realizing a manual closing and release button. Itis expedient in this respect when the spring clip extends along anoutside of the housing cover. It is particularly advantageous when thehousing cover is resilient in specific portions so that a force can beexerted on the spring clip from outside of the housing.

Further details and developments of the invention are indicated in thedependent claims.

The invention will be elucidated in more detail hereinafter by way of anembodiment illustrated in the drawings in which

FIG. 1 shows a load-disconnecting switch according to the invention,with the housing cover being partly cut open, in a three-dimensionalrepresentation;

FIG. 2 shows the load-disconnecting switch of FIG. 1 in a longitudinalsectional view; and

FIGS. 3A, 3B show the load-disconnecting switch in two functional phasesin a longitudinal sectional view.

FIG. 1 gives an outline of a load-disconnecting switch according to theinvention, in which the three-dimensional representation reveals part ofthe magnet system through the partly cut open housing cover. The membersof the load-disconnecting switch are arranged on a base 1. A housing capor cover 2 is slid over the arrangement and, together with base 1,constitutes a closed housing. There are two connecting conductors 3extending out of housing 1 and 2, to which the load circuit of a vehiclemay be connected. Housing cover 2 has two resilient push portions 4through which the load-disconnecting switch may be manually switched onand off. Of the magnetic circuit of the load-disconnecting switch, acoil 5, an armature 6, a core 7, a yoke 8 and a permanent magnet 9 canbe seen. On the side of coil 5 directed away from armature 6, the yoke 8has a Z-shaped crank such that the cranked portion is arranged parallelto the portion of core 7 projecting from the coil. Between the twoparallel portions of yoke 8 and core 7, there is left a gap receivingthe permanent magnet 9. The possibility of simple mounting of permanentmagnet 9 is an advantage of this construction, since permanent-magneticmaterials are brittle and thus sensitive. The core arrangementconsisting of core 7, permanent magnet 9 and yoke 8 constitutes togetherwith armature 6 a closed magnetic circuit with permanent magnetic fluxcaused by permanent magnet 9. As regards driving of the coil 5, it isprovided that the magnetic flux generated by the coil counteracts, i.e.is opposite to the magnetic flux generated by permanent magnet 9.

Armature 6 is biased to the open position by an armature spring 10. Thelatter is riveted to armature 6 in an upper portion of the same and issupported near the free spring end thereof on a supporting portion 11which in the present embodiment is provided as part of a coil bodyflange. Another possibility of providing a supporting portion would beto extend the yoke 8 to such an extent that the armature spring 10 canbe supported on yoke 8. In that case, the armature 6 possibly would haveto be provided with recesses so that the yoke 8 or yoke portions canproject through the armature.

In an extension, armature spring 10 extends in curved manner around thecoil 5 and is attached on the side of the coil directed away fromarmature 6.

The thus formed spring clip 12 extends parallel to, and spaced closelyfrom, the top side of housing cover 2. By means of the push portions 4,a force can be applied to spring clip 12. In this manner, a manualclosing and release button is realized, with the function thereof beingdescribed hereinafter by way of FIG. 2. In the middle of spring clip 12,a pressure plate 13 is mounted to spring clip 12 such that it is locatedbetween spring clip 12 and the winding of coil 5. In this manner, thespring clip 12 has a firm support at this location, so that a rocker isformed. The push portions 4 for switching on and off are thus clearlyseparated. As an alternative, there may be provided, for example, anadditional flange or web on the coil body that takes over the functionof supporting the spring clip 12. In that event, shrinkage of thewinding package due to aging has no influence on the supporting point ofthe spring clip 12.

FIG. 2 illustrates in addition a contact system. The latter consists ofa contact spring 14 that is mounted on the yoke 8 and carries aswitching contact 15 on its other end. This contact cooperates with afixed contact 16 attached to one of the connecting conductors 3. As theload-disconnecting switch is provided for carrying very high currents,the contact spring is not sufficient to carry this current. Theload-disconnecting switch thus has an additional strand 17 establishinga low-impedance connection to switching contact 15. Another reason foremploying an additional strand 17 consists in that contact spring 14 ismade of a material withstanding the mechanical stress. However,advantageous mechanical properties necessitate that the material be ofrelatively high resistivity. In the mounting region of strand 17 on yoke8, there is provided the connection to the other one of the connectingconductors 3. On the side of armature 6 facing coil 5, armature 6 has alocking lug 18 provided thereon so as to abut an edge 19 of yoke 8 whencontacts 15 and 16 are closed. The locking lug 18 is provided, forexample, as an embossed projection. The armature 6 itself is L-shaped,with the long leg of the L abutting pole areas of core 7 and yoke 8. Thetransverse leg engages under the free end of contact spring 14 orswitching contact 15.

As long as coil 5 is not excited, armature 6 is held in this positiondue to the holding force of permanent magnet 9. Upon excitation of coil5, a magnetic flux is generated in the magnetic circuit which isopposite to the magnetic flux generated by permanent magnet 9 and thusweakens the same. If coil 5 is excited to a sufficient extent, theopening force exerted by armature spring 10 on armature 6 is greaterthan the holding force of permanent magnet 9. Thus, a small air gap isformed between core 7 and armature 6. This air gap effects a strongincrease in magnetic resistance of the magnetic circuit. This causes anabrupt decrease in the holding force, and the armature spring 10 iscapable of completely detaching the armature 6 from core 7 and yoke 8.The gap between armature 6 and yoke 8 increases to such an extent thatthe locking effect between locking lug 18 and yoke 8 is released. A tearspring 20 engaging in a recess of the armature 6 urges the armature 6upwardly, with the armature being no longer retained by the lockingeffect between locking lug 18 and yoke 8. Contact spring 14 and tearspring 20 are made of one piece. During upward movement, the transverseleg of armature 6 pulls switching contact 15 along, so that theconnection between fixed contact 16 and switching contact 15 isseparated.

FIG. 3A illustrates an enlarged section of the load-disconnectingswitch, with contacts 15 and 16 being closed. In FIG. 3B, the contactsystem is shown with open contacts 15 and 16, with locking lug 18 nowabutting the pole area of yoke 8.

The function of the spring clip 12 is understandable from FIGS. 3A and3B as well. If, with contacts 15 and 16 in the open state, a force isapplied to the armature-side half 22 of spring clip 12, which in thepresent embodiment is effected by pressing the corresponding pushportion 4 of housing cover 2, the armature 6 is pushed down. In doingso, contact spring 14 is tensioned via tear spring 20, and switchingcontact 15 and fixed contact 16 contact each other again, so that thecurrent path between the connecting conductors 3 is closed. Armature 6is deflected via the ramp 21 of base 1 such that locking lug 18 movesunder the edge 19 of yoke 8 into the locked position. If pressure isapplied to the half 23 of spring clip 12 remote from the armature, withcontacts 15 and 16 being closed, the spring clip 12 is shifted in thedirection of armature 6, so that armature 6 is released from core 7, thelocking effect is released and the contacts are opened. The resilientdesign of the push portions 4 for actuating the spring clip 12 has theadvantage that there are thus no openings or leaks formed in housingcover 2. For achieving a sealed housing, it is thus only necessary toseal the housing cover 2 with respect to the base 1. This can beachieved by simple casting or sealing.

The operational excitation of the load-disconnecting switch isdetermined by the holding force of the magnet 9 and the tension of thearmature spring 10. For determining a defined operational excitation,there is no mechanical adjustment necessary since an adjustment can beobtained by corresponding magnetization of permanent magnet 9.

What is claimed is:
 1. A load-disconnecting switch, preferably for usein motor vehicles, comprising: a housing have a base and a housingcover, a magnet system having a coil, a core arrangement and anarmature, the core arrangement having a permanent-magnetic sectionexerting a holding force through which the armature is attracted to poleareas of the core arrangement, and said magnet system being adapted tobe excited contrary to said permanent-magnetic section, an armaturespring biasing the armature to an open position, with the holding forceof the permanent-magnetic section with attracted armature being higherthan the spring force of the armature spring, a contact system having acontact spring, a switching contact arranged on the contact spring and afixed contact cooperating with the switching contact, and first andsecond connecting conductors extending out of the housing for connectionof the switching contact and the fixed contact, wherein the armature hasa locking lug engaging a yoke edge of the core arrangement and beingbiased against the yoke edge by a tear spring.
 2. A load-disconnectingswitch according to claim 1, wherein the switching contact is biasedagainst the fixed contact by the contact spring.
 3. A load-disconnectingswitch, preferably for use in motor vehicles, comprising: a housing havea base and a housing cover, a magnet system having a coil, a corearrangement and an armature, the core arrangement having apermanent-magnetic section exerting a holding force through which thearmature is attracted to pole areas of the core arrangement, and saidmagnet system being adapted to be excited contrary to saidpermanent-magnetic section, an armature spring biasing the armature toan open position, with the holding force of the permanent-magneticsection with attracted armature being higher than the sprint force ofthe armature spring, a contact system having a contact spring, aswitching contact arranged on the contact spring and a fixed contactcooperating with the switching contact, and first and second connectingconductors extending out of the housing for connection of the switchingcontact and the fixed contact, and wherein the contact spring has atleast one tear leg engaging said armature and constituting a tearspring.
 4. A load-disconnecting switch, preferably for use in motorvehicles, comprising: a housing have a base and a housing cover, amagnet system having a coil, a core arrangement and an armature, thecore arrangement having a permanent-magnetic section exerting a holdingforce through which the armature is attracted to pole areas of the corearrangement, and said magnet system being adapted to be excited contraryto said permanent-magnetic section, an armature spring biasing thearmature to an open position, with the holding force of thepermanent-magnetic section with attracted armature being higher than thesprint force of the armature spring, a contact system having a contactspring, a switching contact arranged on the contact spring and a fixedcontact cooperating with the switching contact, and first and secondconnecting conductors extending out of the housing for connection of theswitching contact and the fixed contact, wherein the switching contactis connected to the first connecting conductor by an additional strand.5. A load-disconnecting switch, preferably for use in motor vehicles,comprising: a housing have a base and a housing cover, a magnet systemhaving a coil, a core arrangement and an armature, the core arrangementhaving a permanent-magnetic section exerting a holding force throughwhich the armature is attracted to pole areas of the core arrangement,and said magnet system being adapted to be excited contrary to saidpermanent-magnetic section, an armature spring biasing the armature toan open position, with the holding force of the permanent-magneticsection with attracted armature being higher than the spring force ofthe armature spring, a contact system having a contact spring, aswitching contact arranged on the contact spring and a fixed contactcooperating with the switching contact, and first and second connectingconductors extending out of the housing for connection of the switchingcontact and the fixed contact, wherein the armature is substantiallyL-shaped, with a long leg extending in the region of pole areas of thecore arrangement and a transverse leg having its free end engaging themovable part of the contact system so as to open the contacts.
 6. Aload-disconnecting switch, preferably for use in motor vehicles,comprising: a housing have a base and a housing cover, a magnet systemhaving a coil, a core arrangement and an armature, the core arrangementhaving a permanent-magnetic section exerting a holding force throughwhich the armature is attracted to pole areas of the core arrangement,and said magnet system being adapted to be excited contrary to saidpermanent-magnetic section, an armature spring biasing the armature toan open position, with the holding force of the permanent-magneticsection with attracted armature being higher than the spring force ofthe armature sprint, a contact system having a contact spring, aswitching contact arranged on the contact spring and a fixed contactcooperating with the switching contact, and first and second connectingconductors extending out of the housing for connection of the switchingcontact and the fixed contact, wherein the armature spring extendsaround the longitudinal axis of the coil substantially in curved manner,so that a central portion of the armature spring is located close to ahousing wall.
 7. A load-disconnecting switch according to claim 6,wherein the central portion of the armature spring is supported on astationary part of the load-disconnecting switch such that a rocker-likearrangement of the armature spring results.
 8. A load-disconnectingswitch, preferably for use in motor vehicles, comprising: a housing havea base and a housing cover, a magnet system having a coil, a corearrangement and an armature, the core arrangement having apermanent-magnetic section exerting a holding force through which thearmature is attracted to pole areas of the core arrangement, and saidmagnet system being adapted to be excited contrary to saidpermanent-magnetic section, an armature spring biasing the armature toan open position, with the holding force of the permanent-magneticsection with attracted armature being higher than the spring force ofthe armature spring, a contact system having a contact spring, aswitching contact arranged on the contact spring and a fixed contactcooperating with the switching contact, and first and second connectingconductors extending out of the housing for connection of the switchingcontact and the fixed contact, wherein a housing portion close to thecentral portion of the armature spring has resilient properties so thata force applied from outside the housing can be transferred to thecentral portion of the armature spring via said resilient housingportion.